fn main() {
	// in allows to check whether an array or a map contains an element
	nums := [1, 2, 3]
	println(1 in nums) // true
	println(4 !in nums) // true
	m := {
		'one': 1
		'two': 2
	}
	println('one' in m) // true
	println('three' !in m) // true
	
	// it's also useful for writing clearer and more compact boolean expressions
	parser := Parser{}
	if parser.token == .plus || parser.token == .minus || parser.token == .div || parser.token == .mult {
		// ...
	}
	if parser.token in [.plus, .minus, .div, .mult] {
		// ...
	}
}

enum Token {
	plus
	minus
	div
	mult
}

struct Parser {
	token Token
}
